+ objects defined here simply add fields to the relevant context objects.
+
+ There is no traceset specific state yet. It may eventually contains such
+ things as clock differences over time.
+
+ The trace state currently consists in a process table.
+
+ The tracefile level state relates to the associated cpu. It contains the
+ position of the current event in the tracefile (since the state depends on
+ which events have been processed) and a pointer to the current process,
+ in the process table, being run on that cpu.
+
+ For each process in the process table, various informations such as exec
+ file name, pid, ppid and creation time are stored. Each process state also
+ contains an execution mode stack (e.g. irq within system call, called
+ from user mode). */